The present disclosure relates to testing sensor equipment, and more particularly a prognostic for flow sensor bit for motor driven compressor.
Environmental control systems (ECS) are utilized on various types of aircraft for several purposes, such as air supply systems and/or cabin condition systems for the aircraft. For example, components of the ECS may be utilized to remove heat from various aircraft lubrication and electrical systems and/or used to condition aircraft cabin air. The cabin air conditioner includes one or more cabin air compressors (CACs), which compress air entering the system from an outside source or from a ram air system. The compressed air is delivered to an air cycle system and/or a vapor cycle system to bring it to a desired temperature then delivered to the aircraft cabin. After passing through the cabin, the air is typically exhausted to the outside. The CACs may be driven, for example, by air-cooled electric motors.
Pneumatic air conditioning kit (PACK) flow sensors are required to be accurate to +/−6% where failure modes occurring in the sensing hardware can generate unreliable readings. Errors associated with sensor readings can lead to uncertainty of operating points and can further lead to instability of a system. Malfunctioning flow sensors can cause undesirable surges effecting the operation of a compressor, where the surges cause a disruption of the airflow to the compressor. The motors driving these compressors respond to flow sensor readings. High flow sensor readings will cause the motor to throttle back while low flow sensor readings will cause the motor to consume more power while generating excessive airflow. These oscillations lead to inefficiencies in the power used to drive the compressors and further leads to unpredictable airflow from the system.
PACK flow sensors may be equipped with BIT (built-in tests) for determining the operability of the flow sensor, however BIT are unable to detect various failures modes such as those failures that generate high flow readings which can induce a CAC surge. Another technique for detecting malfunctioning flow sensors requires using a redundant flow sensor configuration to determine a sensor drift between sensors. However, the redundant configuration increases the cost of operation and maintenance and further increases the processing and complexity of the system